linux-kernel - Re: [PATCH] VM: Implements the swap-out page-clustering technique

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <87iqtbuez9.fsf@basil.nowhere.org>
Date:	Fri, 05 Sep 2008 11:19:38 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	hamid.jahanjou@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] VM: Implements the swap-out page-clustering technique

"Hamid R. Jahanjou" <hamid.jahanjou@...il.com> writes:

> From: Hamid R. Jahanjou
>
> Implements the idea of swap-out page clustering from *BSD for
> Linux. Each time a candidate page is to be swapped out,
> virtually-nearby pages are scanned to find eligible pages to be
> swapped out too as a cluster. This technique increases the likelihood of
> bringing in related data on a page fault and decreases swap space
> fragmentation in the long run. Currently, Linux searches only
> physically-nearby pages which is not optimal since, over time, physically-
> adjacent pages may become unrelated.
>
> The code can be statically tuned. No benchmarks. I'm not sure whether
> the added complexity is acceptable.

Just some general comments:

First I think virtual swap clustering is a great idea in theory and
long overdue.  Hopefully the numbers will agree.

In general the code would be much nicer if you didn't pass around 
all that much in a structure (which is just a fancy way to have
a function with lots of arguments) Perhaps try to restructure
it a bit to make this smaller? Ideally clustering_info should disappear
or at least get much smaller.

Then continue_search seems to be only set to one value so it 
can be eliminated? Perhaps there is more like this.

I didn't quite understand the "adjust the value of our search by
the allocation order". The allocation order should be normally 0.
I think having a tunable for the cluster sizes would be a good idea.
At some point they might be even device dependent (e.g. on a flash
device you would like to have them roughly erase block sized) 

-Andi

-- 
ak@...ux.intel.com
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/